215 research outputs found
Functionalized Multi-Walled Carbon Nanotube-Reinforced Epoxy-Composites: Electrical And Mechanical Characterization
Full text linkCarbon nanotubes (CNTs) got great attention because of their interesting physical and mechanical properties. Due to these interesting properties observed at the nanoscale have motivated scientific community to utilize CNTs as reinforcement in composite materials. In the present study, different CNTs and epoxy nano-composites with different wt% (1, 2, 3, and 4%) of f-MWCNTs were prepared and their surface morphology and orientation has been investigated in detail. Further, the surface investigation, electrical and mechanical tests were carried out on CNTs-filled and unfilled epoxy at maximum sonication time 30 minute to identify the loading effect on the properties of the materials. Experimental results depicts well dispersion of f-MWCNTs, significant improvement that the resistivity of pure epoxy decreased from 108 .m to average value 103 .m with 1, 2, 3, and 4wt% f-MWCNTs. The 4.5wt% CNTs/epoxy was attributed to poor dispersion of f-MWCNTs in the nanocomposte. The hardness of nanocomposite loading 1, 2, 3, 4wt% of CNTs, increased 20.7%, 23.02%, 25.62%, 29.09% respectively as compared to pure epoxy. We believe that our strategy for obtaining CNT–reinforced epoxy nanocomposites is a very promising technology and will open a new doors in fields of aviation, aerospace, marine and sporting goods
Thermal Performance Evaluation of Seawater Cooling Towers
Get PDFSeawater has been used for long time as a cooling fluid in heat exchangers to reduce fresh water usage in industry and power plants. The thermophysical properties of seawater are different from those of fresh water due to the salt content or salinity. This difference is sufficient to affect the heat and mass transfer processes which in turn change the thermal performance. Thermal design of fresh water cooling towers is described in detail in many textbooks and handbooks. However, only a rule of thumb is frequently used for designing of seawater cooling towers. This rule recommends degrading the tower performance by approximately 1% for every 10,000 ppm of salts in the feed water. In this paper, the thermal performance of seawater cooling towers is presented using a detailed model of counterflow wet cooling towers which takes into consideration the coupled simultaneous heat and mass transfer processes and uses state-of-the-art seawater properties from the literature. The model governing equations are solved numerically and the validity of this model is checked using new experimental data that has been measured using a bench top counterflow seawater cooling tower. The effect of the variation of seawater salinity as well as other operating conditions on the effectiveness and Merkel number is investigated.Center for Clean Water and Clean Energy at MIT and KFUP
SONOGRAPHIC FINDINGS IN FEMALES OF REPRODUCTIVE AGE WITH ACUTE PELVIC PAIN
Get PDFBackground: Acute pelvic pain can result from the gynecological, urological systems and/or gastrointestinal. Ultrasound can be used as an initial imaging modality in the evaluation of acute pelvic pain. To determine sonographic findings in females of reproductive age coming with acute pelvic pain. Objective: To determine Sonographic findings in females of reproductive age with acute pelvic pain. Methodology: Toshiba Xario ultrasound machine with a standard gray scale and Doppler ultrasound convex probe of 3.5 MHz – 7.5 MHz or trans-vaginal probe of 5 MHz - 7.5MHz is used. Both transvaginal and trans-abdominal probes were used in this study. The study was conducted at Ultrasound University Clinic, Township, Lahore. Data of 163 patients was collected through convenient sampling. Statistical software for social sciences (SPSS version 22.0) is used for the analysis of data. Results: A total of 163 patients were examined in the study. The age incidence of the cases in this study varied between 15 years to 45 years. The mean age of the patients in the study was 29.8712 years. The uterine fibroid is most commonly involved in acute pelvic pain and is seen in 30.1% cases followed by simple ovarian cyst in 20.2% cases, hemorrhagic cyst in 14.1% cases. 8.6% cases with pelvic pain have no abnormal sonographic findings. Adenomyosis, PID and endometrial polyp in 4.3% each. Endometrial hyperplasia in 3.1%. Follicular cyst, simple adnexal cyst and complex adnexal cyst in 1.8% each, followed by ovarian endometrioma in 0.6% cases and dermoid cyst in 0.6%. In obstetric patients of acute pelvic pain; RPOCs are most common, constituting 1.8% of total acute pelvic pain, molar pregnancy in 1.2%, ectopic pregnancy in 0.6% patients, subchorionic bleed in 0.6% cases. Conclusion: Ultrasound is a very good modality for acute pelvic pain, as it can easily diagnose and characterize the causes of pelvic pain. The wide availability, radiation free and cost effectiveness makes it a first line investigation in acute pelvic pain. In the present study, the most common cause of pelvic pain is uterine fibroid. Key words: Ultrasound (US), Pelvic inflammatory disease (PID), acute pelvic pain, retained products of contraceptives (RPOCs), pouch of Douglas (POD). DOI: 10.7176/JHMN/71-14 Publication date: February 29th 202
Exergoeconomic optimization of a shell-and-tube heat exchanger
Get PDFThe paper presents an economic optimization of a STHX with two commonly adopted (i.e., Kern and Bell-Delaware) and one rarely explored (i.e., Wills-Johnston) methods. A detailed numerical code concerning thermal, hydraulic, exergy, and economic analysis of STHX is developed for all three methods. Normalized sensitivity analysis, parametric study, and Genetic Algorithm are used to ascertain the most influential parameters and optimize the total cost. It is observed that the calculations made using the Wills-Johnston method were reasonably close to the Bell-Delaware method. While the Kern method showed a significant deviation in the shell side calculations because of the several assumptions in this method. The parametric analysis showed that increasing the mass flow rate and the number of baffles increased the operating cost because of an exponential increase in the pressure drops. Finally, the optimization reduced the heat transfer area by ~26.4%, capital cost by ~20%, operational cost by ~50%, total cost by ~22%, and the stream cost by ~21%
Comparison of fouling propensity between reverse osmosis, forward osmosis, and membrane distillation
Get PDFResistance to fouling is often cited as an advantage of emerging desalination technologies such as forward osmosis and membrane distillation over the widely-used reverse osmosis process. However, the nature and magnitude of differences in fouling behavior between these three processes are not well characterized. This study directly compares the fouling and scaling behavior of reverse osmosis (RO), forward osmosis (FO), and direct contact membrane distillation (MD) in the same membrane module under identical hydrodynamic conditions (flux and cross-flow velocity). Fouling experiments were conducted using calcium sulfate as a model inorganic foulant and alginate as a model organic foulant. Although all three processes tolerated some degree of feed supersaturation for 36 h without inorganic fouling (scaling), FO exhibited the greatest scaling resistance, withstanding a feed of 33 ± 2 mM CaSO₄ (approximately twice saturation) without significant flux decline. Scaling occurred at similar concentrations at the membrane between MD and RO; however, while MD tolerated a more concentrated bulk feed due to reduced concentration polarization, flux decline after fouling was considerably more severe in MD. In contrast, MD tolerated organic fouling much better than FO or RO: despite accumulating a similar quantity of alginate gel over 18 h of operation, flux declined only 14% in MD versus 46–47% in RO and FO. These results are explained with respect to differences in temperature, membrane materials, and transport mechanisms between the three processes. Although FO and MD each exhibited superior resistance to one type of foulant, neither process outperformed RO in resistance to both organic and inorganic fouling. These findings inform a more nuanced approach to process selection for the treatment of complex water sources. Keywords: Desalination; Forward osmosis; Fouling resistance; Membrane distillation; Reverse osmosi
A new age of leadership in academia: Need for change and innovation during COVID-19
Get PDF© The Author(s) 2025.The aim of this study is to explore the role of academic leadership and adaptive leadership on organizational readiness for change. During times of pandemic, adaptive leadership has emerged as a vital leadership discipline along with academic leadership due to uncertainty and sensitivity of situation. In addition, demand of innovative behavior has also increased over the years particularly during Covid-19. The study has been carried out in Higher Education Institutions of Pakistan where the data was collected from deans, directors and head of departments in two phases. Quantitative research strategy was opted for the study. Survey research design was followed to respond objectives of the study. The purpose behind the selection of senior academicians is to draw empirical results from the perspective of all the heads of their relevant departments. The data was collected from seven public sector universities across Pakistan. About 251 responses were found valid. Covariance based SEM was used to analyze the data. Analysis reveals a positive and direct relationship between academic and adaptive leadership and organizational readiness for change and similar results were found by placing innovative behavior as a mediator leading to the acceptance of all developed hypotheses. This study is unique in nature and has implications for leaders in academia in terms of unleashing the potential toward uncertain situation in higher education institutions. Study’s major limitation include less representation of the Pakistan as whole country as it included Punjab province only for data collection.Unfunde
Exergoeconomic and Normalized Sensitivity Analysis of Plate Heat Exchangers: A Theoretical Framework with Application
Get PDFHeat exchangers are the mainstay of thermal systems and have been extensively used in desalination systems, heating, cooling units, power plants, and energy recovery systems. This chapter demonstrates a robust theoretical framework for heat exchangers investigation based on two advanced tools, i.e., exergoeconomic analysis and Normalized Sensitivity Analysis. The former is applied as a mutual application of economic and thermodynamic analyses, which is much more impactful than the conventional thermodynamic and economic analyses. This is because it allows the investigation of combinatory effects of thermodynamic and fiscal parameters which are not achieved with the conventional methods. Similarly, the Normalized Sensitivity Analysis allows a one-on-one comparison of the sensitivity of output parameters to the input parameters with entirely different magnitudes on a common platform. This rationale comparison is obtained by normalizing the sensitivity coefficients by their nominal values, which is not possible with the conventional sensitivity analyses. An experimentally validated example of a plate heat exchanger is used to demonstrate the application of the proposed framework from a desalination system
Optimizing the Energy Recovery Section in Thermal Desalination Systems for Improved Thermodynamic, Economic, and Environmental Performance
Get PDFIntegration of energy recovery section with thermal desalination systems improves their performance from thermodynamics, economics, and environmental viewpoints. This is because it significantly reduces input energy, heat transfer area, and capital cost requirements. Above all, the system outlet streams can achieve thermal equilibrium with the environment by supplying heat for useful preheating purposes thus reducing the environmental impacts. The plate heat exchangers are generally employed for this purpose as preheaters. The current paper presents a comprehensive investigation and optimization of these heat exchangers for thermal desalination systems applications. An experimentally validated numerical model employing Normalized Sensitivity Analysis and Genetic Algorithm based cost optimization is developed to investigate their performance at assorted operating conditions. The analysis showed that the heat transfer coefficient, pressure drop, and outlet water cost were improved by an increase in feed flow rate. However, with an increased flow rate, the comprehensive output parameter (h/ΔP) decreased due to the high degree increase in pressure drop. Moreover, an increase in the chevron angle reduced the heat transfer coefficient, pressure drop, and water cost. Finally, the optimization lowered the heat transfer area by ~79.5%, capital investment by ~62%, and the outlet cost of the cold stream by ~15.7%. The operational cost is increased due to the increased pressure drop but the overall impact is beneficial as Ctotal of equipment is reduced by ~52.7%
A comprehensive design and optimization of an offset strip-fin compact heat exchanger for energy recovery systems
Get PDFEnergy recovery in conventional thermal systems like power plants, refrigeration systems, and air conditioning systems has enhanced their thermodynamic and economic performance. In this regard, compact heat exchangers are the most employed for gas to gas energy recovery because of their better thermal performance. This paper presents an economic optimization of a crossflow plate-fin heat exchanger with offset strip fins. A detailed software-based numerical code for thermal, hydraulic, economic, and exergy analysis is developed for three fin geometries. Genetic Algorithm, parametric, and normalized sensitivity analyses are used to discover the most influential parameters to optimize the total cost. The parametric study showed that with the increase of mass flow rates and plate spacing, outlet stream cost and operating cost increased due to the rise in pressure drops. Finally, the optimization reduced the operational cost by ∼78.5%, stream cost by ∼64.5%, and total cost by ∼76.8%
Thermodynamic analysis of humidification dehumidification desalination cycles
Get PDFHumidification–dehumidification desalination (HDH) is a promising technology for small-scale
water production applications. There are several embodiments of this technology which have
been investigated by researchers around the world. However, from a previous literature [1], we
have found that no study carried out a detailed thermodynamic analysis in order to improve and/
or optimize the system performance. In this paper, we analyze the thermodynamic performance
of various HDH cycles by way of a theoretical cycle analysis. In addition, we propose novel high performance variations on those cycles. These high-performance cycles include multi-extraction,
multi-pressure and thermal vapor compression cycles. It is predicted that the systems based on these
novel cycles will have gained output ratio in excess of 5 and will outperform existing HDH systems.King Fahd University of Petroleum and MineralsCenter for Clean Water and Clean Energy at MIT and KFUP
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